1. Field of the Invention
The invention relates to an ignition timing control apparatus for an engine provided with a variable valve mechanism which changes an opening/closing characteristic of an intake valve (at least one of an opening timing and a closing timing).
2. Description of the Related Art
In general, a variable valve mechanism includes at least one of a variable valve timing mechanism which changes a valve timing of an intake valve, and a maximum valve lift amount variable mechanism which changes the maximum valve lift amount of the intake valve. Japanese Patent Application Publication No. JP 2001-263015 A discloses a variable valve mechanism which includes both of the variable valve timing mechanism and the maximum valve lift amount variable mechanism.
In an engine including such a variable valve mechanism, a temperature and a pressure in a combustion chamber are changed according to a change in an opening/closing characteristic. Accordingly, in order to maintain a good combustion state, it is necessary to set an ignition timing considering a change in the temperature and the pressure in the combustion chamber.
However, an ignition timing control apparatus has not been proposed, which sets an ignition timing considering a relationship between the opening/closing characteristic of the intake valve, and the temperature and the pressure in the combustion chamber.